Apparatus for providing high quality power

ABSTRACT

There is provided a system that includes (a) a power feed that distributes a high DC voltage in a building, where the high DC voltage is in a range of about 300 to 600 VDC, (b) a converter, coupled to the power feed, that receives the high DC voltage, and scales the high DC voltage to a low DC voltage, and (c) a controller that controls a firing rate of the converter so that the low DC voltage is in a range of about 23 to 48 VDC.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 10/700,076, filed Nov. 3, 2003, now U.S. Pat. No. 7,141,894which claims priority to U.S. Provisional Patent Application No.60/423,127 filed Nov. 1, 2002 and U.S. Provisional Patent ApplicationNo. 60/453,235 filed Mar. 10, 2003. The content of each of theabove-noted applications is herein incorporated by reference in itsentirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject disclosure relates to systems for providing high qualitypower, and cooling and more particularly to an improved system forproviding uninterrupted DC power for the telephone communications, dataprocessing and industrial equipment.

2. Background of the Related Art

Traditionally, AC commercial power has been used as the primary powersource for a wide variety of applications such as computers, dataprocessing equipment, telephony circuitry and other solid statetechnology devices. Despite this proliferation of the use of AC power,various problems are well-known. For example, U.S. Pat. Nos. 4,277,692;5,126,585; and 5,483,463 disclose practices for improving theperformance of AC power devices. Despite these improvements, manydrawbacks to the AC power still have not been overcome. In particular,AC power must still be converted to DC power for consumption by themajority of solid state devices. Many AC power systems require batterybackup and second 100% rated redundant feeds and are still inefficientat supplying the necessary power and redundancy. Further, the safetyrisk, bulkiness and expense of distributing AC power is well documented.

Many have always considered DC to be more efficient and reliable.However, the prior ability to produce DC power and scale distributionthereof has been a hurdle yet to be overcome. Typically, chemicalbatteries and rectifiers are utilized to produce, distribute and backupcritical DC power. Batteries in such applications have many limitations.When the batteries age, capacity reduces to the point of requiringreplacement that creates a disposal problem. Further, the ability toproduce and draw large amounts of power from a DC battery system isdependant upon the amount and size of the batteries and require largedistribution systems as DC distribution systems are oversized for DCvoltage drop. Modern technology demands more power, requiring a higherconcentration of DC power to reach a higher level of operation.

Despite these and other drawbacks, use of chemical batteries has beenwidely used in to produce and store 48V DC power, in telecommunicationcenters and to provide an alternative backup source for AC voltagesystems during power outages in data centers. For example, see U.S. Pat.No. 5,010,469 to Bobry, in which batteries are used and which isincorporated by reference herein in its entirety to the extent that itdoes not conflict with the present disclosure. Moreover, switchingbetween sources is a recognized problem and often incurs momentarylapses in provision of the power needed. For example, see U.S. Pat. No.5,057,697 to Hammond et al. which is incorporated by reference herein inits entirety to the extent that it does not conflict with the presentdisclosure.

In the past no technology has been available to economically produce anddistribute highly reliable high capacity DC power for use in bothcenters. The use of DC quality power is much more reliable, inexpensiveand would result in tremendous saving of power so it would be extremelydesirable to extensively utilize scaleable DC power. However, as aresult of not being able to scale DC power much like an AC transformerfor distribution, technology dependent upon ready access to DC power hasstagnated. Therefore, a system is needed to produce DC voltage that ishighly reliable, scalable and economical utilizing AC and DC componentswithout the use of chemical storage batteries.

Moreover, prior art systems have required large amounts of wiring andconditioning equipment for electrically interconnecting the AC voltagesource with the load. Typically, the electrical interconections arequite bulky and require a large amount of copper. In data center andtelco applications, switch mode power supplies (“SMPS”) on the serversare fed by AC but have the capability of being powered by DC only.Theses AC driven SMPS generate heat and draw significant power and arevery inefficient. As a result of the high heat generation and a limitedamount of cooling capacity, data processing equipment must be spread outto facilitate proper cooling, therefore data centers have less space forprocessing equipment and an overall decreased cooling load efficiency.Thus, there is a need for a system which provides the necessary powerand can be interconnected with relatively small interconnections andoperate without SMPS in order to increase the efficiency of the datacenter.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to utilize either 208-480incoming volts AC three phase power to produce 23-48VDC outgoing voltageand current for supply throughout a data center or comparable facility.

It is another object of the present disclosure to utilize one AC utilityand emergency power source, preferably a generator, as the incoming mainand emergency feeds to make the system reliable in case of a utilitypower outage.

In one embodiment, the system cycles through a transfer switch withoverlap transition to utility, optional. The transfer switch will takeone emergency and one utility and will switch between the two wheneither manually initiated or loss of utility power has occurred. Thegenerator will feed a distribution panel sized to power a bridge dioderectifier, house loads and air conditioning, utilizing 480/3/60 inputand 300-600 VDC output. The rectifier will be designed to reduce DCripple. In another embodiment, the system will utilize a flywheelbattery-less DC power supply source, in parallel to the output of a mainrectifier, to generate 300-600 VDC and tie into the output of therectifier. The system utilizes DC output power from the rectifier tocharge the flywheel. When AC power is lost to the main rectifier input,the flywheel will discharge the kinetic storage into the load side ofthe rectifier until such time that the emergency generator has startedand has taken over the critical load. When the emergency source is online it will supply power to both the load and will also recharge theflywheel device to 100% preparing the system for the eventual return toutility. Upon the return or stabilization of utility power consistentlyfor a set period, the transfer switch will retransfer the system load tothe utility. During this transfer, the break in the system power willonce again be bridged by the flywheel source in the opposite direction.

Preferably, the 300-600 VDC from the output of the main rectifier willdistribute throughout the facility reducing both the wire size and thecurrent necessary to run a Power Converter Unit or PCU that will stepthe high voltage down to useable 23-48 VDC to power plants or computersthat are designed to utilize 23-48 volts DC. Thereby allowing thecomputers to be supplied without a customary switch mode power supplytherefore reducing the inefficiencies of the SMPS saving energy of up to30% and reducing wiring circular mill, reducing cooling requirements,rid the plant of chemical storage batteries and reduce its equipmentinfrastructure required spacing and significantly increasing the powerreliability. This attribute will allow more of the critical indoorsquare footage to be utilized for the electronics necessary to increasebusiness.

In another embodiment, at certain determined interval areas, dependantupon loading and distance, a specially designed DC-to-DC converter, orPower Converter Unit (“PCU”), utilizing intergate bi-polar transistor(hereinafter “IGBT”) technology, redundant power supplies or 30 kWdrawers and a 5-20 kHz DC controller that both senses and fires an IGBTwill be placed. The PCU can be fed by up to two totally independentpower systems providing highly reliable outage protection. Additionally,the PCU is highly resistant to faults and once again adding to the highquality power output. The IGBT will efficiently convert line side DChigh voltage to secondary low side voltage remaining efficient andtightly controlled throughout the potential voltage drop on the primaryside down to 300 VDC. This PCU is much like a DC to DC transformer. Fromthe output of the IGBT device, voltage and current will be distributedto local or close devices that utilize 48 volts DC without the issues ofvoltage drop and excessive heat produced by the SMPS. This voltage canbe controlled by remotely placing a sensor at the furthest device fromthe converter.

Another highly important concept to this power quality system is theutilization of a sophisticated cooling system to rid the space of theheat produced by the efficient delivery of power by the PCU to thetelecommunications and data processing loads. The PCU will deliver powerto racks where the technology will reside. Virtually all of thedelivered power will be utilized by electronic loads. These loads willturn this power completely into heat. Technology today is attempting tocompact as many devices in as small a space as possible. In order toprovide for this condition, a Power Cooling rack (PCR) will be providedthat can liquid cool a plate fin heat exchanger located in the bottom ofthe rack as well as variable speed fans that will efficiently meter airand will cool the computers in the rack up to 20 kW. The best devicebeing utilized today can rid the space of up to 5-7 kW. These racks willprovide for dual fed 48 volt DC distribution for protection againstpower outage of one of the sources increasing reliability.

It should be appreciated that the present disclosure can be implementedin numerous ways, including without limitation as a process, anapparatus, a system, a device or a method. These and other uniquefeatures of the system disclosed herein will become more readilyapparent from the following description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that those having ordinary skill in the art to which the disclosedsystem appertains will more readily understand how to make and use thesame, reference may be had to the drawings wherein:

FIG. 1 is a schematic view of a stationary module constructed inaccordance with the subject invention.

FIG. 2 is a schematic view of a mobile module constructed in accordancewith the subject invention.

FIG. 3 is a schematic view of a third module constructed in accordancewith the subject invention.

FIG. 4 is a perspective view of an enclosure for providing DC power andcooling in accordance with the subject invention.

FIG. 5 is a schematic view of a connected DC conversion unit FIG. 4 inaccordance with the subject invention.

FIG. 6 is a schematic of a diode bridge constructed in accordance withthe subject invention.

FIG. 7 is a block diagram of a system that provides a highly reliablelow DC voltage to a load.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention overcomes many of the prior art problemsassociated with power supplies. The advantages, and other features ofthe system disclosed herein, will become more readily apparent to thosehaving ordinary skill in the art from the following detailed descriptionof certain preferred embodiments taken in conjunction with the drawingswhich set forth representative embodiments of the present invention andwherein like reference numerals identify similar structural elements.

Referring to FIG. 1, an enclosure 110 is utilized to protect the system100 from the elements as well as provide the proper internal environmentnecessary for the component pieces to function properly. Thisenvironment is preferably 40-104 degrees F., non-condensing. In apreferred embodiment, the enclosure 110 is an ECOBAY™ enclosureavailable from Sanmina-SCI Corp. of 2700 North First Street, San Jose,Calif. 95134. The system 100 is designed to be stationary or fixed. Theenclosure 110, when stationary, will house all components with theexception of the DC converters. Such a system 100 would typically beutilized in the larger power applications where the 300-600 VDCdistribution is sent into the facility (not shown) and powers localizedDC converters that step down from 600 to 23-48 VDC. The system 100 willprovide an AC power feed that will supply AC three-phase power to airconditioning units within the facility so the enclosure 110 will beconsidered a self-contained total critical power solution for thefacility.

Preferably, generator 112 will be mounted on the outside of theenclosure 110 in an adjacent environmentally designed container 114. Thecontainer 114 will mount on extended rails that protrude from the bottomof the enclosure 110. The generator 112 includes a sub-base fuel supply116 and will start on a signal from an automatic transfer switch (ATS)118 located inside the enclosure 110. Typically the generator 112 uses afuel cell or turbine unit sized from 250 kW or larger as required by theapplication and supplies 208-480 or high VAC three phase. The generator112 has an output breaker (not shown) and will store up to 12 hours ormore of fuel in the sub-base fuel supply 116. The sub-base fuel supply116 can also be supplied with natural gas to provide for automaticreplenishment. The system 100 can be designed to run in a prime energymode producing inexpensive clean power to the facility, thereby reducingthe overall energy usage. By prime energy mode, the system 100 generatespower and utilizes the heat by-product to power chillers that cool thesystem 100. The system 100 can be used stand alone or coupled inparallel for providing additional capacity and/or reliability.

The ATS 118 is preferably sized from 400 to 1200 amps for a VACthree-phase three-wire. Suitable ATSs 118, without limitation, aredisclosed in U.S. Pat. Nos. 4,761,563 and 5,646,833, each of which isincorporated herein by reference in its entirety. The ATS 118 ispreferably mechanical in nature and fed from two separate sources. Onesource of power to the ATS 118 is the building utility feed and theother is the feed from the generator 112. The utility, or normal feed,is preferably connected through a twist lock or lug configuration 120and is terminated to the normal side of the ATS 118. The generator 112feeds to the emergency side of the ATS 118.

Upon a power outage, the ATS 118 sends a startup signal to the generator112 and, upon reaching the set voltage, mechanically breaks the utilityfeed and connects the emergency source supply power, i.e., fromgenerator 112, to the distribution panel 122. This system 100 can beprovided with overlap transfer if required and follows the sameprocedure in reverse when utility is returned. The system 100 canreceive a remote start or stop signal and can be utilized in either aprime or standby mode.

The distribution panel 122 distributes 208-480, three-phase three-wire,AC power to all of the component devices. The distribution panel 122includes a main breaker and smaller distribution breakers, preferablymolded case, and are of comparable size and fusing to the ATS 118. A20-40 kVA transformer 124 is utilized for house power, i.e. lighting,heating, cooling and the like.

A main rectifier, i.e., rectifier 126, takes a 208 volt through mediumvoltage three-phase feed and produces an output voltage of 300-600 VDC.The sizing range is preferably from 150 kW to 500 kW or as required.Ripple current is minimized by the use of reactors. A DC flywheel 128can take either AC or DC power to spin up a kinetic flywheel and storeenergy until such time that the DC output power feed drops below themain rectifier voltage. At a set point, the DC flywheel 128 dischargesthe stored energy in the form of DC voltage and current to supplyconsistent power to PCUs 130, providing enough time to allow thegenerator 112 to come up to speed and take over the utility feed.

Once the utility power source becomes operational again, the DC flywheel128 will bridge the transfer back to utility in a similar fashion. Afterthe generator 112, or the utility feed has returned and is powering theload, the DC flywheel 128 recharges the kinetic flywheel, in the form offlywheel speed, in readiness to bridge the next power outage. Theflywheel system is preferably an enclosed system. In large applications,the DC flywheel 128 is underground and sized in the megawatt range. Itwill be appreciated by those of ordinary skill in the art that the DCflywheel 128 may be a plurality of kinetic flywheels that are connectedin parallel to form the DC flywheel 128.

DC disconnects (DCDS) or breakers, e.g., DC disconnects 132, fuse thePCUs 130. The DC disconnects 132 are sized to accept voltage drop in theevent that the voltage output by the flywheel goes below recommendedparameters. For example, an unacceptable flywheel voltage drop may occurif the generator 112 miss-starts and must continue to attempt to startand come up to line voltage. As the kinetic flywheel reduces in speedthe output voltage drops. As the flywheel voltage drops, the currentrises in order to maintain the power output at a constant level.

A pair of PCUs 130 receive power from the rectifier 126. The PCUs 130reduce the high voltage output by the rectifier 126 for outputting thedesired voltage to run the load, i.e., solid state technology devices.In smaller applications such as the 50 kW version illustrated, the PCUs130 are housed in the enclosure 110. In larger applications such as 150kW, the PCUs 130 may be located within the building as close to the loadas possible. Preferably, the PCUs 130 can be dual fed and have a numberof outputs. The PCUs 130 have an N+1 control and power configuration. Ina preferred embodiment, the PCUs 130 convert 300-600 VDC to useable23-48VDC. The PCUs 130 have a high frequency sensing and control circuitfor controlling the firing of the IGBTs therein. In controlling theIGBTs in this manner, the physical size of the PCUs 130 is drasticallyreduced and the efficiency significantly increased. For example, seeU.S. Pat. No. 5,646,833.

It is envisioned that the enclosure 110 can be stored outdoors. In theoutdoor application, the 48VDC output by the PCUs 130 connects to thebuilding via twist lock quick connection points 134. The output of thePCUs 130 can also be connected to a common feed point either within thebuilding or out at the enclosure 110, to produce a 2+N configuration.Preferably, remote sensors (not shown) are placed at the furthest loadpoint for providing input to the system 100 to maintain the 48VDC outputat the furthest utilization point. The system 100 also includes ageneral purpose panel 138 for allowing access to house power for otherapplications.

Referring to FIG. 2, as will be appreciated by those of ordinary skillin the pertinent art, a mobile system 200 utilizes the same principlesof the system 100 described above. Accordingly, like reference numeralspreceded by the numeral “2” instead of the numeral “1”, are used toindicate like elements. The mobile system 200 is designed to allow easymovement from one area to another so that high quality power can bequickly made accessible in the area of need. The mobile system 200houses air conditioners, i.e., AC 239, and all the components, and theoutput voltage is sent into the facility from the enclosure 210.Typically, the mobile system 200 is used in a smaller demand applicationof 1000-1500 amps VDC.

Referring to FIG. 3, as will be appreciated by those of ordinary skillin the pertinent art, an expanded system 300 utilizes the sameprinciples of the systems 100 and 200 described above. The system 300utilizes cross-feeding stand-alone converters in order to insurereliable delivery of power. Accordingly, like reference numeralspreceded by the numeral “3” instead of the numerals “1” or “2”, are usedto indicate like elements whenever possible. The system 300 is adaptedand configured to supply power to a data center (not shown). Typically,data centers require power that is conditioned and backed up by anuninterruptible power supplies (hereinafter “UPS”), batteries, orgenerators. Power distribution units (hereinafter “PDU”) typicallydistribute 480 volt three-phase power. For use, the power may betransformed to usable 120/208 volt power. The system 300 is an expandedapplication to meet the needs of a data center.

For redundancy, the system 300 includes a pair of power modules 301A and301B, a pair of distribution panels, 332A and 332B, and a pair of PCUs330A and 330B. PCU 330A houses a pair of DC converter units 331A1 and331A2, and similarly, PCU 330B houses a pair of DC converter units 331B1and 331B2. The power modules 301A, 301B include a generator 312A, 312B,respectively, either prime or standby, that could also be one or morefuel cells or a turbine. In an energy saving mode, wherein the generator312A, 312B or utility source utilizes natural gas to produce electricalpower, the byproduct heat of the generation is utilized to powerabsorption chillers that are, in turn, used to cool the data center, orthe PCUs 330A, 330B. Preferably, the PCUs 330A, 330B accept chilledwater as a cooling medium, e.g., load curtailment.

The PCUs 330A, 330B are located inside the data center as close to the48VDC load as possible. This will allow the rectification of the ACpower to DC for distribution outside of the data center in a remotelocation, thereby saving valuable data center space. The use oftransformers and associated alternating current apparatus is no longernecessary; as a result, the data center is less electronicallyintensive. In another embodiment, the need for SMPS on the servers canbe eliminated and the servers run on DC voltage supplied in a centralpower feed scenario by the system 300. The elimination of SMPSsignificantly reduces the overall heat and power draw and by virtue ofreducing power and cooling space is freed up or can be more denselydesigned to accommodate more equipment per square foot. The PCUs 330A,330B in a 2+N scenario can be applied and can simply and effectivelyprovide the computers with reliable power meeting or exceeding the stateof the art 3 to 5 nines availability requirements. In short, the datacenter is less electronically intensive due to the replacing of theAC-DC back to AC topologies of the UPS as well as eliminating thesophistication and expense of the AC sine wave reconstruction,synchronization and paralleling electronics. The system 300 inconjunction with a PCR saves installation expense, operating expense incooling, and infrastructure space necessary for all of the required ACpower equipment.

In a preferred embodiment, the system 300 produces a distribution DCvoltage of 600VDC from outside of the data center. Typically, the sizingof the system 300 could be up to 2 MW. The 600VDC is produced by arectification system 326A, 326B with a DC flywheel 328A, 328B forproviding transition to a backup generator 312A, 312B as explainedabove. It is envisioned that the conversion for the data centerapplication from 600-48VDC is accomplished using the PCUs 330A, 330B ata sizing of roughly 150 kW.

Each PCU 330A, 330B can receive two 600VDC power feeds, i.e., one fromeach of the power modules 301A, 301B, so that if a single power module301A or 301B malfunctions, the 48VDC output of the system 330 ismaintained. The distribution panel 332A is between the power module 301Aand the PCU 330A, and similarly, the distribution panel 332A is betweenthe power module 301B and the PCU 330B. The distribution panels 332A and332B have DC breakers or fuses 335A1, 335A2, 335B1 and 335B2, utilizedto protect the inputs of the DC converter units 331A1, 331A2, 331B1 and331B2.

FIG. 4 shows an embodiment of a PCR 444 that houses a PCU 430 thatincludes a plurality of DC converter units 431. PCR 444 will eliminatethe heat produced by PCU 430 or computers installed into the PCR 444,through the utilization of local chilled water supply and chilled waterreturn piping (not shown). PCR 444 has a dual role as the housing andcooling apparatus for the PCU 430 as well as cooling racks for computertechnology installed into the free standing racks within the PCR 444.The PCR 444 has a lineup of racks that provide power, cooling andstructural requirements for the computer systems therein. The rackswater cool the DC converter units 431, thus allowing more technology inthe space without the requirement of separate air conditioning units,reducing even further the floor space necessary to support the computersin the data or telecommunications processing area.

PCR 444 is suitable for providing DC power to a commercial building. PCR444 has two doors 402 a, 402 b for providing access to an interiorthereof. Behind door 402 a, the PCR 444 houses a plurality of DCconversion units 431 and, behind door 402 b, a load (not shown). Alsoenclosed in each rack is a chilled water cooling coil (not shown) and aplurality of variable frequency drive fans (not shown) that cool theinternal air in the PCR 444 so that heat from the power or computerdevices is rejected into the water. In the preferred embodiment shown,the PCR 444 has six DC converter units 431 of 30 kW capacity each. As aresult, the PCR 444 can serve as a redundant 150 kW DC power source.

FIG. 5 is a schematic view of an exemplary DC conversion system 505connected to dual power sources 401A and 401B. As can be seen, the highvoltage DC (for example 525 VDC) is distributed relatively easily andefficiently, and near or at the point of consumption, the voltage levelis reduced to a usable level (for example 48VDC). Four 525 VDC powerfeeds 403 a-d provide input power to the DC conversion system 505. 525VDC power feeds 403 a and 403 d are connected to power modules 401A and401B, respectively. The power modules 401A and 401B utilize similarprinciples as systems 100, 200 and 300. Thus, for simplicity, nosignificant discussion of the theory and operation is repeated again. Ofnote, the power modules 401A and 401B each include dual high DC voltagesources, namely a rectifier 426A or 426B, and a flywheel system 428A or428B, in order to increase the available duration and load capacity ofpower during the interim mode. 525 VDC power feeds 403 b and 403 c areconnected to alternate power sources 407. The alternate power sources407 are preferably traditional utilities. In other embodiments, thealternate power sources 407 are fuel cells, batteries, UPS, othergenerators, additional power modules similar to power modules 401A and401B, and combination thereof.

Still referring to FIG. 5, the DC conversion system 505 includes two I/Oboards 440 a, 440 b. The I/O boards 440 a, 440 b act to direct the inputpower to adjacent PCUs 430 a, 430 b. I/O board 440 a receives 525 VDCpower feeds 403 a and 403 b. I/O board 440 b receives 525 VDC powerfeeds 403 c and 403 d. Each I/O board 440 a, 440 b routes the respectivetwo 525 VDC power feeds (403 a and 403 b, or 403 c and 403 d) through adiode bridge 450 (see FIG. 6). The diode bridge 450 is for maintaining aconsistent output regardless of the polarity on the inputs to diodebridge 450. As a result, for example, if 525 VDC power feed 403 amalfunctions (and 525 VDC power feeds 403 b and 403 c also malfunction,for that matter), the proper amount of power is still available to allowPCUs 430 a and 430 b to produce sufficient power to run the load. Theredundancy of two PCUs 430 a, 430 b that are each fed by two 525 VDCpower feeds 440 a and 440 b, or 440 c and 440 d, respectively, whereineach 525 VDC power feed 440 a-d is derived from a different source,results in a highly robust and reliable system.

Each PCU 430 a and 430 b produces sufficient power to run the load. Inturn, the output from the PCUs 430 a and 430 b is routed through aplurality of power cooling racks 444A-F. The PCRs 444A-F connect therespective outputs of the PCUs 430 a and 430 b via another diode bridge(not shown) in order to allow a single functioning PCU 430 a or 430 b tosufficiently power the load. The PCRs 444A-F also distribute the powerto the load, i.e. the technologies or computers in the PCRs 444A-F. Thepower enters the PCRs 444A-F through 48 VDC power feeds 405 a, 405 b. Adiode bridge (see FIG. 6) within the PCRs 444A-F receives 48 VDC powerfeeds 405 a, 405 b so that only one of the 48 VDC power feeds 405 a, 405b needs to be operable in order for the system to provide power.

Each of the PCUs 430 a and 430 b generates significant heat that needsto be removed to insure proper operation. The PCRs 444A-F are watercooled but it will be appreciated that other methods of cooling arepossible as would be appreciated by those of ordinary skill in the artbased upon review of the subject disclosure. In a well-known manner,each PCU 430 a or 430 b may be replaced or reconfigured to allow varyingthe capacity and performance of the PCRs 444A-F to suit the particularapplication.

FIG. 7 is a block diagram of a system 700 that provides a highlyreliable low DC voltage to a load 745. System 700 includes high DCvoltage sources 705, 710, 715 and 720, DC-to-DC converters 725 and 735,controllers 730 and 740, and bridges 708, 718 and 742.

High DC voltage source 705 provides a high DC voltage 706 to bridge 708,and high DC voltage source 710 provides a high DC voltage 707 to bridge708. Bridge 708 couples high DC voltage 706 and high DC voltage 707 toprovide a redundant high DC voltage feed 709 to DC-to-DC converter 725.Bridge 708 maintains a consistent output for redundant high DC voltagefeed 709 so that even if one of high DC voltage source 705 or high DCvoltage source 710 fails, high DC voltage feed 709 will still beoperational. Each of high DC voltage 706, high DC voltage 707, and thevoltage on high DC voltage feed 709 are in a range of about 300 to 600VDC.

High DC voltage source 715 provides a high DC voltage 716 to bridge 718,and high DC voltage source 720 provides a high DC voltage 717 to bridge718. Bridge 718 couples high DC voltage 716 and high DC voltage 717 toprovide a redundant high DC voltage feed 719 to DC-to-DC converter 735.Bridge 718 maintains a consistent output for redundant high DC voltagefeed 719 so that even if one of high DC voltage source 715 or high DCvoltage source 720 fails, high DC voltage feed 719 will still beoperational. Each of high DC voltage 716, high DC voltage 717, and thevoltage on high DC voltage feed 719 are in a range of about 300 to 600VDC.

DC-to-DC converter 725 utilizes an IGBT to scale the high DC voltagefrom high DC voltage feed 709 to a low DC voltage 726. Controller 730controls a firing rate of DC-to-DC converter 725 so that low DC voltage726 is in a range of about 23 to 48 VDC.

DC-to-DC converter 735 utilizes an IGBT to scale the high DC voltagefrom high DC voltage feed 719 to a low DC voltage 736. Controller 740controls a firing rate of DC-to-DC converter 735 so that low DC voltage736 is in a range of about 23 to 48 VDC.

Bridge 742 couples low DC voltage 726 and low DC voltage 707 to providea redundant low DC voltage feed 743 to load 745. Bridge 742 maintains aconsistent output for redundant low DC voltage feed 743 so that even ifone of low DC voltage 726 or low DC voltage 736 becomes unavailable, lowDC voltage feed 743 will still be operational.

While the invention has been described with respect to preferredembodiments, those skilled in the art will readily appreciate thatvarious changes and/or modifications can be made to the inventionwithout departing from the spirit or scope of the invention.

1. A system comprising: a first power feed that distributes a first highDC voltage in a building, wherein said first high DC voltage is in rangeof about 300 to 600 VDC; a first converter, coupled to said first powerfeed, that receives said first high DC voltage, and scales said firsthigh DC voltage to a first low DC voltage; a first controller thatcontrols a firing rate of said first converter so that said first low DCvoltage is in a range of about 23 to 48 VDC; a second power feed thatdistributes a second high DC voltage in said building, wherein saidsecond high DC voltage is in a range of about 300 to 600 VDC; a secondconverter, coupled to said second power feed, that receives said secondhigh DC voltage, and scales said second high DC voltage to a second lowDC voltage; a second controller that controls a firing rate of saidsecond converter so that said second low DC voltage is in a range ofabout 23 to 48 VDC; a bridge that couples said first and second low DCvoltages to provide a low DC voltage feed, wherein said low DC voltagefeed provides power at a level that is about equal to a sum of (a) powerprovided by said first converter and (b) power provided by said secondconverter; and first and second sources for said first and second highDC voltages, respectively, each of said first and second high DC voltagesources comprises a rectifier that receives an AC voltage and convertssaid AC voltage to a high DC voltage.
 2. The system of claim 1, whereinsaid first and second high DC voltage sources each further comprises aflywheel that stores energy, and that discharges said energy to providea high DC voltage.
 3. The system of claim 2, wherein said AC voltage isin a range of about 208 to 480 VAC.
 4. The system of claim 1, whereinsaid first and second high DC voltage sources each further comprises adevice selected from the group consisting of a rectifier, a fuel cell, abattery, an uninterruptible power supply and a generator.
 5. The systemof claim 1, wherein each of said first and second converters providesgreater than or equal to about 30 kW of power.